When environmental protection is emphasized, the computer industry is required to produce computers that have a reduced environmental impact, such as a green computer. The most standard of green computers is a computer that has reduced power consumption.
Methods that may be used to control the central processing unit (CPU) are described as follows. The first method is the SpeedStep technology developed for controlling mobile CPUs by Intel. The basic principle of this method is that a mobile CPU runs at a speed virtually identical to that of a desktop system when the notebook computer is connected to an AC outlet. When powered by a battery, the processor drops to a lower frequency and voltage, conserving battery life while maintaining a high level of performance. In other words, the mobile CPU runs at different speeds as appropriate for different power sources. For example, a mobile CPU of 1.8 GHz frequency is powered by a 1.3V operation voltage and runs at 1.8 GHz when the notebook computer is connected to an AC outlet. In contrast, this mobile CPU is powered by a 1.2V operation voltage and runs at 1.2 GHz to reduce power consumption when the notebook computer is powered by a battery. In other words, the SpeedStep technology automatically reduces the operation speed of the mobile CPU to extend battery life when a battery is used as the power source. However, the SpeedStep technology developed by Intel does not support desktop CPUs.
Another method that may be used by both a mobile CPU and a desktop CPU is a throttling technology. This technology performs a throttling function inside the CPU. FIG. 1 shows an example of the CPU performing the throttling function. In a duty cycle, the operation system can generate a policy to run the processor at a predetermined ratio such that the performance is less than the maximum performance. This policy may run the CPU in accordance with the state of the operation system. As shown in FIG. 1, the throttling function mechanism provides the operation system with the functionality to run the CPU at a special percentage of a duty cycle. In other words, the temperature of the CPU will increase if the CPU keeps running at full speed. At this time, the operation system automatically slows down the CPU to reduce the temperature of the CPU. For example, the operation system generates a policy to automatically adjust the CPU to run at a special percentage, such as 50%, of a duty cycle if the temperature reaches the highest limit. The operation system adjusts the CPU again until the temperature of the CPU is acceptable to keep running for the whole duty cycle. This throttling function ensures that the computer system performs well. However, the main goal of this method is the thermal control of the CPU. Dynamically changing the performance in accordance with the requirements of the computer system is therefore difficult with this method.
Use of a desktop CPU in a notebook computer is an effective method of reducing the cost and increasing the performance. Such application of desktop CPUs in notebook computer is however hindered by the high heat generation and power consumption of the desktop CPU. The SpeedStep technology described above and developed by Intel can be directly controlled by Win XP developed by Microsoft. This SpeedStep technology permits the operation system to adjust the operation speed of the CPU to reduce the power consumption in accordance with its condition. However, desktop CPUs developed by Intel do not support this function.
A way of reducing the cost of notebook computers and the power consumption of desktop CPU is therefore required. Such a reduction is further constrained in that it must preserve the existing hardware framework while resolving the above problems.